THz Generation Process in LT-GaAs Optical down-conversion is the most successful commercial technique for THz generation using Low temperature grown GaAs (LT-GaAs). The technique is often known as Terahertz Time-Domain Spectroscopy (THz-TDS). This technique works by optical pulse excitation of a photoconductive switch. Here, a femtosecond laser pulse illuminates a gap between two electrodes (or antenna) printed on a semiconductor substrate, see figure 1. The laser pulse creates electrons and holes which are then accelerated by the applied bias between the electrodes, this transient photocurrent, which is coupled to an antenna, contains frequency components that reflect the pulse duration, hence generating an electromagnetic wave containing THz components. In a THz-TDS setup, the THz radiation is detected using a receiver device which is identical to the photoconductive switch emitter, and it is gated by the same optical pulse. For Figure 1, please click below: The main reason behind using LT-GaAs is the attractive properties of this material for ultrafast photoconductive application. LT-GaAs has unique combination of physical properties including: short carrier lifetime (< 200 fs), high resistivity, high electron mobility and high break down field. Low temperature growth of GaAs (between 190-350 C) allows excess arsenic to be incorporated as point defects: arsenic antisite (which represents the majority of the defects), arsenic interstitial and gallium vacancies. Ionised antisite defects which act as deep donors, approximately 0.7 eV bellow the conduction band, provide fast trapping for electrons from the conduction band to mid-gap states (0.7eV). Due to this fast trapping of electrons by arsenic atisite defects, as-grown LT-GaAs may have carrier life time as short as 90 fs. This enhances electron-hole recombination leading to a substantial decrease in the electron lifetime, hence making the LT-GaAs suitable for THz generation.For Figure 2, please click below: News from Samir Rihani Remark: Powerway wafer can offer LT-GaAs, size from 2" to 4", epi layer can be up to 3um, micro defect density can be <5/cm2,carrier lifetime can be <0.5ps

The AlGaN/GaN power FET is an aluminum gallium nitride (AlGaN)/gallium nitride (GaN) field effect transistor (FET) fabricated on an inexpensive silicon. The transistor uses Panasonic's own crystal growing technology and GaN materials that have over 10 times the breakdown voltage and below 1/5 lower resistance of existing silicon (Si). As a result, it has achieved a 350 V breakdown voltage, same as Si power metal-oxide-semiconductors (MOS), a very low specific on-state resistance of 1.9 m Ohm cm2 (below 1/10 of Si power MOS), and high-speed power switching of less than 0.1 nanosecond (below 1/100 of Si power MOS). The transistor also has a current handling capability of 150 A (over five times that of Si power MOS). Just one of these new transistors can substitute more than 10 parallel-connecting Si power MOSFETs, contributing significantly to power savings and miniaturization of electronic products. By adopting silicon substrates, the material cost is drastically reduced to less than 1/100 of silicon carbide (SiC) power MOSFETs. The new AlGaN/GaN power FET is the result of development of Panasonic's source-via-grounding (SVG) structure technology where the transistor source electrode is connected to the Si substrate through holes formed on the surface side. This eliminates source wires, bonding and pads from the substrate surface. Consequently, the chip size and wire inductance are significantly reduced. An AlN/AlGaN buffer layer grown at a high temperature and an AlN/GaN multi-layer film are used on the first layer to reduce defect density on the Si substrate and improve the heterojunction interface quality. Panasonic developed the GaN growth technology in partnership with Professor Takashi Egawa of the Research Center for Nano-Device and System, Nagoya Institute of Technology. The new technology has been vital in making the new high power AlGaN/GaN FET. By successfully growing GaN on an Si substrate, Panasonic responded, for the first time in the world, to the needs for low-loss switching devices that combine both high breakdown voltage and low specific on-state resistance. It was becoming increasingly difficult for current Si power MOSFETs to fulfill the needs. Source:phys.org For more information, please visit our website: www.semiconductorwafers.net, send us email at angel.ye@powerwaywafer.com or powerwaymaterial@gmail.com

Indium arsenide films have been grown by an electrodeposition process at low temperature on a tin oxide (SnO2) substrate. X-ray diffraction studies showed that the as-grown films are poorly crystallized and heat treatment improved the crystallinity of InAs films. Atomic force microscopic measurements revealed that the InAs film surface is formed by particles for which the grain size depends on the electrolysis parameters; we have found that the grain size increases with the electrolysis current density. Absorption measurements show that the band gap energy red-shifts with increasing particle size. This result can be interpreted as a consequence of the quantum confinement effect on the carriers in the nanocrystallites. Source:IOPscience For more information, please visit our website: http://www.semiconductorwafers.net, send us email at angel.ye@powerwaywafer.com or powerwaymaterial@gmail.com

Cree (NASDAQ:CREE) is a leading innovator of lighting-class light emitting diodes (LEDs), LED lighting and semiconductor solutions for wireless and power applications. The company is committed to drive LED adoption by optimizing performance and shrinking the gap between LED lighting and conventional technology. Cree currently accounts for 7.7% of the global LED market, but we estimate its share to rise to over 10% over our review period. A surplus in LED supply led by Chinese manufacturers and a consequent decline in prices are key trends currently plaguing the LED industry. However, witnessing an increase in orders for all its business divisions, Cree claims that the LED market dynamics are improving. LEDs require significantly lower energy and maintenance costs compared to traditional lighting sources. Historically, the LED market has grown at a CAGR of 21% from 2007 to 2008, whereas Cree’s revenue witnessed a CAGR of 25%. We estimate the global LED market to grow at a CAGR of 9% until the end of our forecast period with the general LED lighting market growing at a faster pace. After the acquisition of Ruud Lighting, Cree has become one of the leading providers of indoor and outdoor LED lighting. Thus, we forecast growth in Cree’s LED revenue (13% CAGR till 2019) to outpace growth in the global LED market. Cree derives over 70% of its valuation from the LED market and any variation from our estimate can lead to a significant impact on its valuation. Our price estimate of $35 for Cree is at a considerable discount to the current market price. In this article we discuss our rationale behind Cree’s likely LED market share gains in the coming years. Growth Potential In The LED Market; LED Sales To Increase At A CAGR Of 9% The LED market has more than doubled in size in the last 5 years from $5 billion in 2006 to approximately $14 billion in 2012. Many economies, especially in emerging markets, are witnessing rapid urbanization, which is leading to greater opportunities for economic and social development. However, the same creates resource scarcity and raises environmental concerns. Countries are starting to recognize the opportunity LEDs provide to help them significantly reduce their energy costs and lower maintenance charges. With energy savings of 50%-60% leading to lower greenhouse gas emissions and a much higher lifespan compared to conventional technologies, LEDs offer a cost effective option to lower global electricity consumption. In major market segments – such as commercial, industrial and outdoor lighting – LEDs have only 10% market penetration, whereas in the residential sector (perhaps the most promising) the penetration stands at a mere 1%. [1] We estimate the global market to grow at a CAGR of 9% going forward and reach over $25 billion by the end of our forecast period. China’s LED Market Is Growing At A Fast Pace; Cree Expanded Its Manufacturing Facilities In The Region China, Europe, Japan, South Korea, Taiwan and the United Stat...